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Most batteries are around 90-95% efficient. Electrical motors are around 85-90% as well. So that isn't that bad. Of course most hydrogen vehicles are actually
by jillesvangurp 3y ago
Most batteries are around 90-95% efficient. Electrical motors are around 85-90% as well. So that isn't that bad.
Of course most hydrogen vehicles are actually battery electrical vehicle where the battery is charged by the fuel cell. Reason for this is that fuel cells are not that easy to throttle up and down and typically have a lower output than the maximum input of the motor. So, you put enough battery in between the fuel cell and the motor so that you don't run out of energy when e.g. driving up a mountain. Also this enables benefiting from things like regenerative braking. Technically, you could take any hydrogen vehicle and convert it to pure battery electric by simply replacing the hydrogen bits and bops with a bigger battery. No need to change the drive train or anything else. It already is a battery electric vehicle.
So a hydrogen car or truck inherits all those supposed (in)efficiencies of battery electric and then adds the additional (in)efficiencies of the hydrogen production, storage, transport, and fuel cell conversion. The whole process starts with the same renewable energy that you would otherwise put straight into the battery. So these are additional inefficiencies that go on top of the whole end to end chain. The further away you are from where the hydrogen is produced, the worse it gets.
Anyway, when you multiply all of these efficiencies, you end up with a good reason why hydrogen cars are not a great idea from a cost point of view. Just a lot of losses in this long chain of energy conversions that you necessarily have to do that multiply to lots of energy loss.
What this article proposes is super interesting of course but it doesn't change the math for transport. Battery electric is inherently more efficient. It works today and it's going to only get better. Cheaper more dense batteries, cheaper renewable energy production, etc. There are plenty of more sensible/economical uses for hydrogen outside transport.
- qwytw 3y ago>Most batteries are around 90-95% efficient. Electrical motors are around 85-90% as well. So that isn't that bad. I guess you'd also have take into account loss during transmission (which seesm to vary wildly between 2-10% depending on location) and charger efficiency. IIRC if we add it all up it's about 70%.
- _hypx 3y agoWith renewable energy, you will have to deal with intermittency too. That requires energy storage and more transmission losses.
- _aavaa_ 3y agoPumped hydro is a well established technology with a round trip efficiency ~75%. As for the cars, they can we can install chargers at all parking spots and take advantage of the intermittent energy during the day to charge the cars then. Many colder climates have engine blocker heater outlets as a standard feature for outdoor parking, adding 120V or 240V chargers to new parking spots (and retrofitting old ones) is not a far fetched idea.
- jillesvangurp 3y agoThat two is share by hydrogen, which again just adds to this. So, it doesn't change the math. Everything downstream of the fuel cell is not something you can avoid and any improvements you make there benefit BEVs with and without a fuel cell. The key thing to focus on here is how much the fuel cell adds in terms of inefficiencies.
- _hypx 3y agoThis entirely ignores the problem of intermittency. The wind does not blow all the time and the sun does not shine all the time. To solve this, you will need grid energy storage. The problem is that adds significant energy losses for a hypothetical car powered purely by renewable energy. In fact, it could be even greater than what it takes to power a hydrogen car. That is immediately obvious when you realize that the energy storage system is hydrogen in the first place. Ultimately, people are just demonizing the inefficiencies of the hydrogen process while totally ignoring real-world losses for battery cars.
- _aavaa_ 3y agoIt is not demonizing to say that electric cars have a round trip efficiency of ~80% while round trip efficiencies for electrolosys->storage->fuel cell for anything outside of a lab is in the mid 30%.
- _hypx 3y agoExcept you are ignoring energy storage losses for BEVs. Take that into account and it drops to the same level as doing it with hydrogen. It also helps to stop living in the past with hydrogen. Efficiencies are significantly better than you are admitting.
- _aavaa_ 3y agoWhich energy storage losses am I ignoring? Perhaps mid 30% are living in the past. Do you have a reference for the round trip efficiency of a production hydrogen car?
- _hypx 3y agoWe’ve already had this conversation before. I’m not interested in repeating myself. You already have the knowledge the grasp the truth, provided you have any interest in doing so.